While unpack zip archive sqldeveloper-18.4.0-376.1900-no-jre.zip I got error "Warnings: Headers Error". I use 7-zip unarchiver.
Checked hash sum.
On website: Windows 32-bit/64-bit SHA1: 2536dad95e0390f7202f0c5962a1af99ee3de787
My result is: SHA1: 2536DAD95E0390F7202F0C5962A1AF99EE3DE787
Checksum is OK.
PS: But it's all ok with previous version sqldeveloper-18.3.0.277.2354-no-jre.zip